156 NATURAL HISTORY OF SELBORNE. 



hirundines alone seem to be annoyed with dipterous insects, which 

 infest every species, and are so large, in proportion to themselves, 

 that they must be extremely irksome and injurious to them. 

 These are the hippoboscce hirundinis, with narrow subulated wings, 

 abounding in every nest ; and are hatched by the warmth of the 

 bird's own body during incubation, and crawl about under its 

 feathers. 



"A species of them is familiar to horsemen in the south of 

 England under the name of forest-fly ; and to some of side-fly, 

 from its running sideways like a crab. It creeps under the tails, 

 and about the groins, of horses, which, at their first coming out 

 of the north, are rendered half frantic by the tickling sensation ; 

 while our own breed little regards them. 



"The curious Reaumur discovered the large eggs, or rather 

 pupa, of these flies as big as the flies themselves, which he hatched 

 in his own bosom. Any person that will take the trouble to 

 examine the old nests of either species of swallows may find in 

 them the black shining cases or skins of the pupce of these insects ; 

 but for other particulars, too long for this place, we refer the 

 reader to 'L'Histoire d'Insectes' of that admirable entomologist. 

 Tom. iv., pi. ii." 



